A U.S. Marine helicopter carrying 37 Marines on maneuvers crashed in an isolated mountain region on South Korea's southeast coast early today, and 22 were killed, U.S. authorities said. Fifteen Marines were injured, some critically, when the Sikorsky Sea Stallion crashed shortly before 7 a.m. south of the industrial port city of Pohang and 250 miles southeast of Seoul, a Marine Corps spokesman said.

Sikorsky Aircraft is studying the feasibility of building civilian helicopters capable of carrying up to 100 people on short- and medium-range flights, the company announced. The new helicopters would be introduced around the turn of the century and could help ease growing problems with urban transportation and airport congestion, officials said Saturday.

A study of helicopter noise in the city, prompted by residents' complaints that began in earnest when flights were stepped up during the Olympics, has concluded that the main source is the California National Guard, which operates a fleet of 100 helicopters out of the Los Alamitos Armed Forces Reserve Center. However, National Guard Col.

Seven men were killed and 11 others injured in the crash of two military helicopters during separate training maneuvers, authorities said Saturday. An Army Blackhawk helicopter crashed Friday night during a training exercise in a densely wooded area of Ft. Chaffee, Ark., killing five of the 13 soldiers who were on board.

At the same time that the Reagan Administration was opening a secret arms pipeline to Iran, it was granting permission for a major defense contractor to supply helicopter parts to the Tehran government, the company has confirmed. It was the first known instance that the Ayatollah Ruhollah Khomeini's regime successfully tapped into U.S. commercial channels for critically needed aircraft parts. United Technologies Corp., in a statement issued Friday from its Hartford, Conn.

Iranian President Ali Khamenei said Tuesday that his forces will block all oil movement in the Persian Gulf if its tankers are stopped, the Iranian news agency IRNA reported. If Iran fails to export its oil, "there would be no way for any other country to do the same through the waterway," IRNA, monitored in Nicosia, quoted him as saying.

A Santa Ana man was among 15 Marines injured in the fatal crash of a military helicopter in South Korea, but his family said Tuesday that the serviceman is in good spirits and is expected to recover quickly from his injuries. The Marine Corps on Tuesday released the names of 34 servicemen killed or injured in the crash Monday of a military helicopter in South Korea, including eight from California.

The pilot of the Navy aircraft that plucked Marines from stormy seas minutes after their Tustin-based helicopter went down near Ventura County said Thursday they were lucky to have ditched so close to a search and rescue base. A ninth Marine remained missing and is presumed drowned. He was identified Thursday as Jeffrey B. Johns, 22, an avionics technician from Uniontown, Ohio. Lt. Robert Moore said in a telephone interview from Pt.

The Pentagon has ordered that 181 military helicopters--including about 50 stationed at the Tustin Marine Corps Helicopter Air Station and the El Toro Marine Corps Air Station--be grounded for 10 weeks to six months because of defective parts that could cause their rotor blades to snap off during flight, a Navy spokesman said Friday. The 181 Sea Stallion CH-53A and CH-53D helicopters represent about 48% of the copters assigned to the military, said Lt.